In vehicles, electrical machines are used e.g. as a starter for an internal combustion engine or e.g. as a generator for generating electrical power. In modern vehicles, electrical machines are also used as a combination of starter and generator, as so-called “starter generators.” Starter generators are electrical machines that can be operated in a vehicle as an electric motor or as a generator, as required. As a generator, starter generators must be able to take on all tasks conventionally handled by the generator, namely supplying electricity to the vehicle electrical system and charging the vehicle battery. As an electric motor, starter generators must quickly bring the crankshaft of the internal combustion engine up to the necessary starting rotation speed when said engine is started.
Undesired rotation speed oscillations can occur upon shutoff of an internal combustion engine in a vehicle. Such rotation speed oscillations become transferred to the vehicle's body, and this is perceived by vehicle occupants as unpleasant. Such rotation speed oscillations occur in particular, for example, in a start-stop mode in which the internal combustion engine of the vehicle is automatically shut off at a standstill.
German Published Patent Appln. No. 101 23 037 A1 or German Patent No. 60 2004 012 838 T2 disclose, for example, apparatuses or methods for controlled shutoff of an internal combustion engine. Here the rotation speed profile of the internal combustion engine is adapted to a defined rotation speed profile by the fact that a torque is applied to a crankshaft by an electrical machine, with the result that the rotation speed of the internal combustion engine is raised or lowered depending on the situation.
These methods require rapid implementations of the torques to be applied, however, in order to adapt the rotation speed in real time. Such rapid implementations are difficult to realize because of the communication required in the vehicle.
Another possibility would be accurate setting of a rotation speed for the electrical machine, although implementing this in real time is complicated.
It is therefore desirable to describe a capability for preventing or at least reducing, in a simple manner, vibrations upon shutoff of an internal combustion engine which are perceptible to vehicle occupants.